WO2010116823A1 - Optical film, method for producing optical film, liquid crystal panel and image display device - Google Patents

Abstract

Disclosed are: an optical film having improved slipperiness, high dope stability and high suitability for continuous-length production; a method for producing said optical film; a liquid crystal panel using said optical film; and an image display device using said liquid crystal panel. Specifically disclosed is an optical film which comprises 20 to 80 mass% of a cellulose acylate resin and 20 to 80 mass% of an acrylic resin, characterized by containing at least one kind of solvent, selected from an ester solvents, a ketone solvent and an aliphatic solvent, in an amount of more than or equal to 0.1 mass% and less than 1.0 mass%.

Description

Optical film, method of manufacturing optical film, liquid crystal panel, and image display device

The present invention relates to an optical film, a method for producing the optical film, a liquid crystal panel using the optical film, and an image display device using the liquid crystal panel.

Polymethyl methacrylate (hereinafter abbreviated as PMMA), which is a representative of conventional acrylic resins, has been suitably used for optical films from the viewpoint of its excellent transparency, dimensional stability, low hygroscopicity, and the like.

However, the PMMA film has a problem in heat resistance, and it has been found that the slipperiness due to the deposition of plasticizers, additives, etc. on the film surface is inferior depending on the temperature environment during production. Particularly in recent years, slipperiness is an important production characteristic because optical films have become longer and wider. Furthermore, the stability of the dope is indispensable for the production of a long film, but when the dope is left for a long time, the occurrence of precipitates that cause film failure may be observed.

In order to improve heat resistance, a method of adding polycarbonate (hereinafter abbreviated as PC) to an acrylic resin has been proposed, but there are limitations on the solvent that can be used, and the compatibility between resins is insufficient, It became cloudy and the haze increased, making it difficult to use as an optical film (for example, see Patent Document 1).

In addition, a method of introducing an alicyclic alkyl group as a copolymerization component of an acrylic resin, a method of forming a cyclic structure in a molecular main chain through an intramolecular cyclization reaction, and the like are disclosed (for example, Patent Document 2). 3, 4).

However, although these methods can improve heat resistance to some extent, there is still a problem with slipperiness due to deposition of plasticizers, additives, etc. on the film surface that occurs during production.

JP-A-5-306344 JP 2002-12728 A JP 2005-146084 A JP 2007-191706 A

Accordingly, an object of the present invention is to provide an optical film with high slipperiness and good dope stability and high production suitability, a method for producing the optical film, a liquid crystal panel using the optical film, and the liquid crystal panel An object of the present invention is to provide an image display apparatus using the.

The above object of the present invention is achieved by the following configuration.

1. In an optical film containing 20 to 80% by mass of a cellulose acylate resin and 20 to 80% by mass of an acrylic resin,
An optical film comprising 0.1% by mass or more and less than 1.0% by mass of at least one solvent selected from an ester solvent, a ketone solvent, and an aliphatic solvent.

2. A method for producing the optical film according to 1 above,
Cellulose acylate resin and acrylic resin, methylene chloride, alcohol,
A method for producing an optical film, wherein a dope is produced by dissolving in a mixed solvent of at least one solvent selected from an ester solvent, a ketone solvent, and an aliphatic solvent.

3. 2. A liquid crystal panel produced using the optical film described in 1 above.

4. 4. An image display device produced using the liquid crystal panel as described in 3 above.

According to the present invention, an optical film with improved slipperiness and good dope stability and high production suitability, a method for producing the optical film, a liquid crystal panel using the optical film, and the liquid crystal panel The used image display device can be provided.

It is the figure which showed typically the dope preparation process, casting process, and drying process of the solution casting film forming method used for this invention.

Hereinafter, modes for carrying out the present invention will be described in detail, but the present invention is not limited to these.

The present invention contains conventional acrylic resins such as slipperiness deterioration due to deposition of plasticizers, additives, etc. on the film surface that occurs during production due to heat resistance problems, and stability deterioration due to precipitate generation in the dope. The present invention provides a novel optical film in which the defects of the optical film are improved, and a method for producing the optical film.

The inventor blends the acrylic resin (A) and the cellulose acylate resin (B) at a specific ratio and uses a specific solvent to improve the heat resistance and plasticize the film surface. As a result, it has been found that an optical film having a long production suitability with no slippage deterioration due to precipitation of additives, additives, etc. and good dope stability can be obtained.

Hereinafter, the present invention will be described in detail.

<Solvent according to the present invention>
The optical film of the present invention is an optical film containing at least one solvent selected from ester solvents, ketone solvents, and aliphatic solvents.

By containing the acrylic resin (A) and the cellulose acylate resin (B) in a specific ratio and further containing these specific solvents, a plasticizer and an additive are added to the film surface generated during the production due to heat resistance. It is possible to remarkably reduce the deterioration of the slipperiness due to the precipitation, and the generation of precipitates when the dope is left for a long time.

The ester solvent according to the present invention is a solvent having an ester group in the molecule. For example, methacrylic acid and ester derivatives thereof (methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methacrylic acid) i-butyl, t-butyl methacrylate, octyl methacrylate, cyclohexyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, tetrahydrofurfuryl methacrylate, benzyl methacrylate, dimethylaminoethyl methacrylate, methacrylic acid Diethylaminoethyl, etc.), acrylic acid and its ester derivatives (methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, i-butyl acrylate, t-butyl acrylate, orange acrylate) Chill, cyclohexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, tetrahydrofurfuryl acrylate, 2-ethoxyethyl acrylate, diethylene glycol ethoxylate acrylate, 3-methoxybutyl acrylate, benzyl acrylate, Dimethylaminoethyl acrylate, diethylaminoethyl acrylate, etc.), methyl acetate, butyl acetate, ethyl acetate, isopropyl acetate, amyl acetate, isoamyl acetate, ethyl methoxyacetate, ethyl ethoxyacetate, propylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether Acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol Phenyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monopropyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monophenyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, 2-methoxybutyl acetate, 3-methoxybutyl acetate, 4-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, 3-ethyl-3-methoxybutyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, 2-eth Xoxybutyl acetate, 4-ethoxybutyl acetate, 4-propoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentyl acetate, 4-methoxypentyl acetate, 2-methyl-3-methoxypentyl acetate, 3-methyl-3- Methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate, 4-methyl-4-methoxypentyl acetate, propylene glycol diacetate, methyl formate, ethyl formate, butyl formate, propyl formate, ethyl lactate, butyl lactate, propyl lactate, Ethyl carbonate, propyl carbonate, butyl carbonate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, butyl pyruvate, methyl acetoacetate, ethyl acetoacetate, methyl propionate, ethyl propionate, Propyl lopionate, isopropyl propionate, methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, methyl-3-methoxypropionate, ethyl-3-methoxypropionate, ethyl-3-ethoxypropionate, propyl -3-Methoxypropionate and the like can be mentioned, and in the present invention, methyl methacrylate is preferably used.

The ketone solvent of the present invention is a solvent having a ketone group in the molecule. For example, 1-octanone, 2-octanone, 1-nonanone, 2-nonanone, acetone, 4-heptanone, 1-hexanone, 2-hexanone, diisobutylketone, cyclohexanone, methylcyclohexanone, phenylacetone, methylethylketone, methylisobutylketone, acetylacetone, acetonylacetone, ionone, diacetonyl alcohol, acetylcarbinol, acetophenone, methylnaphthylketone, isophorone, propylene carbonate, γ -Butyrolactone and the like can be mentioned, and methyl ethyl ketone is preferably used in the present invention.

Examples of the aliphatic solvent in the present invention include pentane, hexane, octane, decane, 2,2,4-trimethylpentane, 2,2,3-trimethylhexane, cyclohexane and the like, and hexane is preferably used.

At least one solvent selected from an ester solvent, a ketone solvent, and an aliphatic solvent according to the present invention is contained in the optical film in an amount of 0.1% by mass or more and less than 1.0% by mass. When the content is less than 0.1% by mass, the effect of improving the slip property and the dope stability is small, and when the content is 1.0% by mass or more, the stability of the dope is deteriorated and precipitates are increased. In general, an optical film using an acrylic resin contains a monomer component of the acrylic resin, but the content is 1% by mass or more and is not included in the scope of the present invention.

The content of the solvent in the optical film can be measured by the following method.

(Quantification method of solvent content)
The solvent content in the optical film can be quantified by headspace gas chromatography.

In the headspace gas chromatography method, a sample is sealed in a container, heated, and the gas in the container is quickly injected into the gas chromatograph while the container is filled with volatile components, and mass spectrometry is performed to identify the compound. The volatile components are quantified while performing. In the headspace method, it is possible to observe all peaks of volatile components by gas chromatography, and to quantify volatile substances and monomers with high accuracy by using an analysis method using electromagnetic interaction. It can be done together. The following apparatus can be used as an example.

Headspace device: HP7694 Head Space Sampler (manufactured by Hewlett-Packard Company)
Temperature conditions: transfer line 200 ° C, loop temperature 200 ° C
Sample amount: 0.8 g / 20 ml vial GC: HP5890 (manufactured by Hewlett-Packard Company)
MS: HP5971 (manufactured by Hewlett-Packard Company)
Column: HP-624 (30m x 0.25mm ID)
Oven temperature: initial temperature 40 ° C. (holding time 3 minutes), heating rate 10 ° C./min, ultimate temperature 200 ° C. (holding time 5 minutes)
Measurement mode: SIM (select ion monitor) mode <Optical film containing acrylic resin>
First, physical property values of the optical film containing the acrylic resin according to the present invention will be described.

In the optical film according to the present invention, the slip property of the film measured according to the method of JIS K7125-1999 is preferably 0.40 or less, and more preferably 0.30 or less. When the slipping property is in the above range, the handling failure of the long film such as wrinkles and hanging due to the precipitate can be remarkably reduced. The slippage is measured by sampling from drying to winding. As the measuring device, a dynamic friction coefficient friction measuring device TR type (manufactured by Toyo Seiki), UNIVERSAL TESTING MACHINE RH-30, etc. manufactured by Shimadzu Corporation can be used.

In addition, the optical film of the present invention is an optical film containing an acrylic resin that contains an acrylic resin (A), a cellulose acylate resin (B), and the specific solvent according to the present invention and does not cause ductile fracture. preferable.

The above-mentioned ductile fracture is caused by a stress that is greater than the strength of a certain material, and is defined as a fracture that involves significant elongation or drawing of the material before the final fracture. The fracture surface is characterized by numerous indentations called dimples.

Therefore, “an optical film that does not cause ductile fracture” is characterized in that fracture such as fracture is not observed even when a large stress is applied such that the film is folded in two.

The demand for the brittleness of optical films is increasing from the viewpoint of reworkability and productivity as optical films become larger and thinner with the recent increase in liquid crystal display devices, and the above ductile fracture does not occur. Is required.

The optical film according to the present invention has a tension softening point of 105 ° C. when considering use in a high-temperature environment such as a projector having a high haze and a high temperature such as a projector or a vehicle-mounted display device. The temperature is preferably ˜145 ° C., more preferably 110 ° C. to 130 ° C.

As a specific method for measuring the tension softening point temperature of the optical film, for example, a Tensilon tester (ORIENTEC Co., RTC-1225A) is used, and the optical film is cut out by 120 mm (length) × 10 mm (width). The temperature can be increased at a rate of temperature increase of 30 ° C./min while pulling with a tension of 30 ° C., and the temperature at 9 N is measured three times, and the average value can be obtained.

The optical film according to the present invention preferably has a glass transition temperature (Tg) of 110 ° C. or higher. More preferably, it is 120 ° C. or higher. Especially preferably, it is 150 degreeC or more.

The glass transition temperature referred to here is an intermediate value determined according to JIS K7121 (1987) using a differential scanning calorimeter (DSC-7 model manufactured by Perkin Elmer) at a heating rate of 20 ° C./min. Point glass transition temperature (Tmg).

In the optical film according to the present invention, it is preferable that the number of defects within a film plane of 5 μm or more is 1/10 cm square or less. More preferably, it is 0.5 piece / 10 cm square or less, more preferably 0.1 piece / 10 cm square or less.

Here, the diameter of the defect indicates the diameter when the defect is circular, and when it is not circular, the range of the defect is determined by observing with a microscope according to the following method, and the maximum diameter (diameter of circumscribed circle) is determined.

The range of the defect is the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope when the defect is a bubble or a foreign object. When the defect is a change in the surface shape, such as transfer of a roll flaw or an abrasion, the size is confirmed by observing the defect with the reflected light of a differential interference microscope.

In addition, when observing with reflected light, if the size of the defect is not clear, aluminum or platinum is vapor-deposited on the surface for observation.

In order to obtain a film having excellent quality expressed by such a defect frequency with high productivity, it is necessary to filter the polymer solution with high precision immediately before casting, to increase the cleanliness around the casting machine, It is effective to set drying conditions after rolling stepwise and to dry efficiently while suppressing foaming.

When the number of defects is more than 1/10 cm square, for example, when a tension is applied to the film during processing in a later process, the film breaks with the defect as a starting point, and the productivity may be significantly reduced. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

Also, even when visual confirmation is not possible, when a hard coat layer or the like is formed on the film, the coating agent may not be formed uniformly, resulting in defects (coating defects). Here, the defect is a void in the film (foaming defect) generated due to the rapid evaporation of the solvent in the drying process of the solution casting, a foreign matter in the film forming stock solution, or a foreign matter mixed in the film forming. This refers to the foreign matter (foreign matter defect) in the film.

The optical film according to the present invention preferably has a breaking elongation in at least one direction of 10% or more, more preferably 20% or more in the measurement based on JIS K7127-1999.

The upper limit of the elongation at break is not particularly limited, but is practically about 250%. In order to increase the elongation at break, it is effective to suppress defects in the film caused by foreign matter and foaming.

The optical film according to the present invention preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film.

Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact part (cooling roll, calender roll, drum, belt, coating substrate in solution casting, transport roll, etc.) during film formation. It is also effective to reduce the diffusion and reflection of light on the film surface by reducing the refractive index of the acrylic resin.

The optical film according to the present invention preferably has a haze value (turbidity) of less than 0.5%, which is one of the indices representing transparency, but the brightness and contrast when incorporated in a liquid crystal display device. Is more preferably 0.4% or less.

The haze value of the optical film is a value measured according to JIS K7361-1-1997 and JIS K7136-2000.

The film containing the acrylic resin according to the present invention can be preferably used as an optical film as long as it satisfies the physical properties as described above. However, by having the following composition, the film has excellent workability and heat resistance. Can be obtained.

That is, from the viewpoint of achieving both workability and heat resistance, the optical film contains an acrylic resin (A) and a cellulose acylate resin in a mass ratio of 80:20 to 20:80. The excellent effect of the present invention can be obtained.

In the optical film according to the present invention, the acrylic resin (A) and the cellulose acylate resin (B) are contained in a mass ratio of 80:20 to 20:80, preferably 50% by mass of the acrylic resin (A). That's it.

When the acrylic resin component is increased, for example, the dimensional change under high temperature and high humidity is suppressed, and curling of the polarizing plate and warping of the panel when used as a polarizing plate can be remarkably reduced. Further, in a composition having an acrylic resin component of 50% by mass or more, the above physical properties can be maintained for a longer time.

The optical film according to the present invention may include a resin other than the acrylic resin (A) and the cellulose acylate resin (B).

The total mass of the acrylic resin (A) and the cellulose acylate resin (B) is 55 to 100% by mass, preferably 60 to 99% by mass of the optical film.

<Acrylic resin (A)>
The acrylic resin used in the present invention includes a methacrylic resin. The resin is not particularly limited, but a resin comprising 50 to 99% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable therewith is preferable.

Examples of other copolymerizable monomers include alkyl methacrylates having 2 to 18 alkyl carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, alkyl acrylates such as acrylic acid and methacrylic acid. Saturated acids, maleic acids, fumaric acids, divalent carboxylic acids containing unsaturated groups such as itaconic acid, aromatic vinyl compounds such as styrene, α-methylstyrene, and nucleus-substituted styrene, α, β- such as acrylonitrile, methacrylonitrile, etc. Examples thereof include unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, and glutaric anhydride, and these can be used alone or in combination of two or more.

Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

The acrylic resin (A) used in the optical film according to the present invention preferably has a weight average molecular weight (Mw) of 80000 to 1000000 from the viewpoint of mechanical strength as a film and fluidity when producing the film.

The weight average molecular weight of the acrylic resin according to the present invention can be measured by gel permeation chromatography. The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

The production method of the acrylic resin (A) in the present invention is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. The polymerization temperature may be 30 to 100 ° C. for suspension or emulsion polymerization, and 80 to 160 ° C. for bulk or solution polymerization. Furthermore, in order to control the reduced viscosity of the produced copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

By using this molecular weight, both heat resistance and brittleness can be achieved.

Commercially available acrylic resins can be used as the acrylic resin according to the present invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Denki Kagaku Kogyo Co., Ltd.) and the like can be mentioned. .

<Cellulose acylate resin (B)>
The cellulose acylate resin according to the present invention may be substituted with either an aliphatic acyl group or an aromatic acyl group, but is preferably substituted with an acetyl group.

When the cellulose acylate resin according to the present invention is an ester with an aliphatic acyl group, the aliphatic acyl group has 2 to 20 carbon atoms, specifically acetyl, propionyl, butyryl, isobutyryl, valeryl, pivaloyl, Examples include hexanoyl, octanoyl, lauroyl, stearoyl and the like.

In the present invention, the aliphatic acyl group is meant to include those further having a substituent. When the aromatic ring is a benzene ring in the above-described aromatic acyl group, the substituent of the benzene ring Are exemplified.

When the cellulose acylate resin is an ester with an aromatic acyl group, the number of substituents X substituted on the aromatic ring is 0 or 1 to 5, preferably 1 to 3, particularly preferably. Is one or two.

Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

The cellulose acylate resin used in the cellulose resin according to the present invention has a structure having a structure selected from at least one of a substituted or unsubstituted aliphatic acyl group and a substituted or unsubstituted aromatic acyl group. Used as structures, these may be single or mixed acid esters of cellulose.

The substitution degree of the cellulose acylate resin according to the present invention is such that the total substitution degree (T) of the acyl group is 2.00 to 3.00, the acetyl group is not necessarily required, and the substitution degree (ac) of the acetyl group is 0. Is 1.89. More preferably, the acyl group substitution degree (r) other than the acetyl group is 2.00 to 2.89.

The acyl group other than the acetyl group preferably has 3 to 7 carbon atoms.

In the cellulose acylate resin according to the present invention, those having an acyl group having 2 to 7 carbon atoms as a substituent, that is, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, It is preferably at least one selected from cellulose acetate benzoate and cellulose benzoate.

Among these, particularly preferable cellulose acylate resins include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

More preferably, the mixed fatty acid is a lower fatty acid ester of cellulose acetate propionate or cellulose acetate butyrate having an acyl group having 2 to 4 carbon atoms as a substituent.

The portion not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

Incidentally, the substitution degree of the acetyl group and the substitution degree of other acyl groups were determined by the method prescribed in ASTM-D817-96.

If the weight-average molecular weight (Mw) of the cellulose acylate resin according to the present invention is 75,000 or more, the object of the present invention can be achieved even if the weight average molecular weight (Mw) is about 1,000,000. Those having 280000 are preferred, and those having 100,000 to 240,000 are more preferred.

<Acrylic particles (C)>
In the present invention, the optical film may contain acrylic particles.

The acrylic particles (C) used in the present invention can be present in the form of particles in the optical film with the acrylic resin (A) and the cellulose acylate resin (B) (also referred to as incompatible state).

The acrylic particles (C) are obtained, for example, by collecting a predetermined amount of the produced optical film, dissolving it in a solvent, stirring, and sufficiently dissolving / dispersing it, so that the pore diameter is less than the average particle diameter of the acrylic particles (C). It is preferable that the weight of the insoluble matter filtered and collected using the PTFE membrane filter is 90% by mass or more of the acrylic particles (C) added to the optical film.

The acrylic particles (C) used in the present invention are not particularly limited, but are preferably acrylic particles (C) having a layer structure of two or more layers, particularly the following multilayer structure acrylic granular composite. It is preferable.

The multilayer structure acrylic granular composite is formed by laminating an innermost hard layer polymer, a cross-linked soft layer polymer exhibiting rubber elasticity, and an outermost hard layer polymer from the center to the outer periphery. This refers to a particulate acrylic polymer having a structure.

Preferred embodiments of the multilayer structure acrylic granular composite used in the present invention include the following. (A) Monomer comprising 80 to 98.9% by weight of methyl methacrylate, 1 to 20% by weight of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, and 0.01 to 0.3% by weight of polyfunctional grafting agent (B) 75 to 98.5% by mass of an alkyl acrylate having 4 to 8 carbon atoms in the presence of the innermost hard layer polymer in the presence of the innermost hard layer polymer, A crosslinked soft layer polymer obtained by polymerizing a monomer mixture comprising 0.01 to 5% by mass of a multifunctional crosslinking agent and 0.5 to 5% by mass of a multifunctional grafting agent; (c) the innermost hard In the presence of a polymer comprising a layer and a crosslinked soft layer, a monomer mixture comprising 80 to 99% by mass of methyl methacrylate and 1 to 20% by mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group is polymerized. Outermost hard layer weight And the obtained three-layer structure polymer is an innermost hard layer polymer (a) 5 to 40% by mass, a soft layer polymer (b) 30 to 60% by mass, and An outermost hard layer polymer (c) comprising 20 to 50% by mass, having an insoluble part when fractionated with acetone, and an acrylic granular composite having a methyl ethyl ketone swelling degree of 1.5 to 4.0 at the insoluble part .

As disclosed in Japanese Patent Publication No. 60-17406 or Japanese Patent Publication No. 3-39095, not only the composition and particle diameter of each layer of the multilayered acrylic granular composite are defined, but also the multilayered acrylic granular composite. By setting the tensile modulus of the body and the degree of swelling of methyl ethyl ketone in the acetone-insoluble part within a specific range, it is possible to realize a further sufficient balance between impact resistance and stress whitening resistance.

Here, the innermost hard layer polymer (a) constituting the multilayer structure acrylic granular composite is 80 to 98.9% by mass of methyl methacrylate and 1 to 20 mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group. % And a monomer mixture consisting of 0.01 to 0.3% by mass of a polyfunctional grafting agent is preferred.

Here, examples of the alkyl acrylate having 1 to 8 carbon atoms in the alkyl group include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like. And n-butyl acrylate are preferably used.

The proportion of the alkyl acrylate unit in the innermost hard layer polymer (a) is 1 to 20% by mass. When the unit is less than 1% by mass, the thermal decomposability of the polymer is increased, while the unit is 20% by mass. If it exceeds 50%, the glass transition temperature of the innermost hard layer polymer (c) is lowered, and the impact resistance imparting effect of the three-layer structure acrylic granular composite is lowered.

Examples of the polyfunctional grafting agent include polyfunctional monomers having different polymerizable functional groups, such as allyl esters of acrylic acid, methacrylic acid, maleic acid, and fumaric acid, and allyl methacrylate is preferably used. . The polyfunctional grafting agent is used to chemically bond the innermost hard layer polymer and the soft layer polymer, and the ratio used during the innermost hard layer polymerization is 0.01 to 0.3% by mass. .

The crosslinked soft layer polymer (b) constituting the acrylic granular composite is an alkyl acrylate having from 9 to 8 carbon atoms having an alkyl group of 1 to 8 in the presence of the innermost hard layer polymer (a). What is obtained by polymerizing a monomer mixture consisting of 10% by mass, 0.01 to 5% by mass of a multifunctional crosslinking agent and 0.5 to 5% by mass of a multifunctional grafting agent is preferred.

Here, n-butyl acrylate or 2-ethylhexyl acrylate is preferably used as the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group.

In addition to these polymerizable monomers, it is possible to copolymerize 25% by mass or less of other monofunctional monomers capable of copolymerization.

Examples of other monofunctional monomers that can be copolymerized include styrene and substituted styrene derivatives. As the ratio of the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group and styrene increases, the glass transition temperature of the produced polymer (b) decreases as the former increases, that is, it can be softened.

On the other hand, from the viewpoint of the transparency of the resin assembly, the refractive index of the soft layer polymer (b) at room temperature is set to the innermost hard layer polymer (a), the outermost hard layer polymer (c), and the hard heat. It is more advantageous to make it closer to the plastic acrylic resin, and the ratio between them is selected in consideration of these.

For example, in applications where the coating layer thickness is small, it is not always necessary to copolymerize styrene.

As the polyfunctional grafting agent, those mentioned in the section of the innermost layer hard polymer (a) can be used. The polyfunctional grafting agent used here is used to chemically bond the soft layer polymer (b) and the outermost hard layer polymer (c), and the proportion used during the innermost hard layer polymerization is impact resistance. From the viewpoint of the effect of imparting properties, 0.5 to 5% by mass is preferable.

As the polyfunctional crosslinking agent, generally known crosslinking agents such as divinyl compounds, diallyl compounds, diacrylic compounds, dimethacrylic compounds and the like can be used, but polyethylene glycol diacrylate (molecular weight 200 to 600) is preferably used.

The polyfunctional cross-linking agent used here is used to generate a cross-linked structure during the polymerization of the soft layer (b) and to exhibit the effect of imparting impact resistance. However, if the above-mentioned polyfunctional grafting agent is used during the polymerization of the soft layer, the polyfunctional crosslinking agent is not an essential component because the crosslinked structure of the soft layer (b) is generated to some extent. Is preferably 0.01 to 5% by weight from the viewpoint of imparting impact resistance.

The outermost hard layer polymer (c) constituting the multi-layer structure acrylic granular composite has a methyl methacrylate of 80 to 99 mass in the presence of the innermost hard layer polymer (a) and the soft layer polymer (b). % And a monomer mixture comprising 1 to 20% by mass of an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group is preferred.

Here, as the acrylic alkylate, those described above are used, but methyl acrylate and ethyl acrylate are preferably used. The proportion of the alkyl acrylate unit in the outermost hard layer (c) is preferably 1 to 20% by mass.

Also, when the outermost hard layer (c) is polymerized, an alkyl mercaptan or the like can be used as a chain transfer agent to adjust the molecular weight for the purpose of improving the compatibility with the acrylic resin (A).

In particular, it is preferable to provide the outermost hard layer with a gradient such that the molecular weight gradually decreases from the inside toward the outside in order to improve the balance between elongation and impact resistance. As a specific method, the monomer mixture for forming the outermost hard layer is divided into two or more, and the molecular weight is increased from the inside by a method of sequentially increasing the amount of chain transfer agent added each time. It is possible to make it smaller toward the outside.

The molecular weight formed at this time can also be examined by polymerizing the monomer mixture used each time under the same conditions, and measuring the molecular weight of the obtained polymer.

The particle diameter of the acrylic granular composite which is a multilayer structure polymer preferably used in the present invention is not particularly limited, but is preferably 10 nm or more and 1000 nm or less, and more preferably 20 nm or more and 500 nm or less. More preferably, it is most preferably 50 nm or more and 400 nm or less.

In the acrylic granular composite that is a multilayer structure polymer preferably used in the present invention, the mass ratio of the core and the shell is not particularly limited, but when the entire multilayer structure polymer is 100 parts by mass, The core layer is preferably 50 parts by mass or more and 90 parts by mass or less, and more preferably 60 parts by mass or more and 80 parts by mass or less.

Examples of such commercially available multilayered acrylic granular composites include, for example, “Metablene” manufactured by Mitsubishi Rayon Co., “Kane Ace” manufactured by Kaneka Chemical Co., Ltd., “Paraloid” manufactured by Kureha Chemical Co., Ltd., Rohm and Haas “Acryloid” manufactured by KK, “Staffyroid” manufactured by Ganz Kasei Kogyo Co., Ltd., “Parapet SA” manufactured by Kuraray Co., Ltd., and the like can be used alone or in combination of two or more.

Further, specific examples of the acrylic particles (c-1) which are graft copolymers preferably used as the acrylic particles (C) preferably used in the present invention include unsaturated carboxylic acids in the presence of a rubbery polymer. A monomer mixture comprising an acid ester monomer, an unsaturated carboxylic acid monomer, an aromatic vinyl monomer, and, if necessary, other vinyl monomers copolymerizable therewith A polymerized graft copolymer may be mentioned.

The rubbery polymer used for the acrylic particles (c-1) as the graft copolymer is not particularly limited, but diene rubber, acrylic rubber, ethylene rubber, and the like can be used. Specific examples include polybutadiene, styrene-butadiene copolymer, block copolymer of styrene-butadiene, acrylonitrile-butadiene copolymer, butyl acrylate-butadiene copolymer, polyisoprene, butadiene-methyl methacrylate copolymer. , Butyl acrylate-methyl methacrylate copolymer, butadiene-ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-isoprene copolymer, and ethylene-acrylic acid Examples thereof include a methyl copolymer. These rubbery polymers can be used alone or in a mixture of two or more.

Further, it is preferable that the refractive index of each of the acrylic resin (A) and the acrylic particles (C) is approximate because the transparency of the optical film according to the present invention can be obtained. Specifically, the refractive index difference between the acrylic particles (C) and the acrylic resin (A) is preferably 0.05 or less, more preferably 0.02 or less, and particularly preferably 0.01 or less.

In order to satisfy such a refractive index condition, a method of adjusting the monomer unit composition ratio of the acrylic resin (A) and / or a rubbery polymer or monomer used for the acrylic particles (C) The refractive index difference can be reduced by a method of adjusting the composition ratio, and an optical film excellent in transparency can be obtained.

The difference in refractive index referred to here means that the optical film according to the present invention is sufficiently dissolved in a solvent in which the acrylic resin (A) is soluble to obtain a cloudy solution, which is subjected to an operation such as centrifugation. The solvent was separated into a soluble part and an insoluble part, and the soluble part (acrylic resin (A)) and the insoluble part (acrylic particles (C)) were purified, and then the measured refractive index (23 ° C., measurement wavelength: 550 nm).

In the present invention, the method of blending the acrylic particles (C) with the acrylic resin (A) is not particularly limited. After the acrylic resin (A) and other optional components are previously blended, usually at 200 to 350 ° C. A method of uniformly melt-kneading with a single-screw or twin-screw extruder while adding acrylic particles (C) is preferably used.

In addition, a solution in which acrylic particles (C) are dispersed in advance is added to a solution (dope solution) in which acrylic resin (A) and cellulose acylate resin (B) are dissolved and mixed, or acrylic particles (C) In addition, a method in which a solution obtained by dissolving and mixing other optional additives is added in-line can be used.

Commercially available acrylic particles (C) used in the present invention can also be used. For example, metabrene W-341 (C2) (manufactured by Mitsubishi Rayon Co., Ltd.), Chemisnow MR-2G (C3), MS-300X (C4) (manufactured by Soken Chemical Co., Ltd.) and the like can be mentioned.

The optical film according to the present invention preferably contains 0.5 to 45% by mass of acrylic particles (C) with respect to the total mass of the resin constituting the film.

<Other additives>
In the optical film according to the present invention, a plasticizer can be used in combination in order to improve the fluidity and flexibility of the composition. Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy.

Of these, polyester-based and phthalate-based plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

In particular, when adipic acid, phthalic acid, or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

The ester plasticizer may be any of ester, oligoester and polyester types, and the molecular weight is preferably in the range of 100 to 10000, but preferably in the range of 600 to 3000, the plasticizing effect is large.

Also, the viscosity of the plasticizer has a correlation with the molecular structure and molecular weight, but in the case of an adipic acid plasticizer, the range of 200 to 5000 mPa · s (25 ° C.) is preferable because of compatibility and plasticization efficiency. Furthermore, some polyester plasticizers may be used in combination.

The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the composition containing the acrylic resin (A). If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use.

The optical film according to the present invention preferably contains an ultraviolet absorber, and examples of the ultraviolet absorber used include benzotriazole, 2-hydroxybenzophenone, and salicylic acid phenyl ester. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones.

Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. be able to.

In addition, since the transition from the thin coating layer to the substrate layer is particularly small and hardly precipitates on the surface of the laminate, the amount of contained UV absorber is maintained for a long time, and the durability of the weather resistance improvement effect is excellent. From the point of view, it is preferable.

Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] Such as til] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine A hybrid system having both structures can be mentioned, and these can be used alone or in combination of two or more. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

Furthermore, various antioxidants may be added to the acrylic resin (A) used in the optical film according to the present invention in order to improve the thermal decomposability and thermal colorability during molding. It is also possible to add an antistatic agent to give the optical film antistatic performance.

For the optical film according to the present invention, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used.

Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphates, halogen-containing condensed phosphonates, halogen-containing phosphites, and the like.

Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl) Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

<Optical film formation>
Although the example of the film forming method of the optical film which concerns on this invention is demonstrated, this invention is not limited to this.

As a film forming method, a production method such as an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, a hot press method, etc. can be used. From the viewpoint of suppression of optical defects, solution casting by casting is preferred.

(Organic solvent)
The organic solvent useful for forming the dope when the optical film according to the present invention is produced by the solution casting method dissolves the acrylic resin (A), the cellulose acylate resin (B), and other additives at the same time. It is preferable.

For example, it is preferable to use a mixed solvent of methylene chloride, which is a chlorinated organic solvent, alcohol, and at least one solvent selected from an ester solvent, a ketone solvent, and an aliphatic solvent according to the present invention.

As the alcohol, a linear or branched aliphatic alcohol having 1 to 4 carbon atoms is preferable, and examples thereof include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Can do.

A dope composition in which at least 15 to 45 mass% in total of three kinds of acrylic resin (A), cellulose acylate resin (B), and acrylic particles (C) are dissolved in the above solvent is preferable.

Hereinafter, a preferable method for forming an optical film according to the present invention will be described.

1) Dissolution step In an organic solution mainly composed of a good solvent for the acrylic resin (A) and the cellulose acylate resin (B), the acrylic resin (A), the cellulose acylate resin (B), and optionally acrylic in the dissolution vessel. The step of dissolving the particles (C) and other additives while stirring to form a dope, or the acrylic resin (A) and cellulose acylate resin (B) solution, in some cases acrylic particle (C) solution, other In this step, the additive solution is mixed to form a dope that is a main solution.

For dissolving the acrylic resin (A) and the cellulose acylate resin (B), a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544 Various melting methods such as a method of performing a cooling dissolution method as described in JP-A-9-95557 or JP-A-9-95538, a method of performing at a high pressure as described in JP-A-11-21379 However, a method in which pressure is applied at a temperature equal to or higher than the boiling point of the main solvent is preferable.

The total amount of the acrylic resin (A) and the cellulose acylate resin (B) in the dope is preferably 15 to 45% by mass. An additive is added to the dope during or after dissolution to dissolve and disperse, then filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

The dope used in the present invention preferably removes foreign substances by filtration, and the filter used for filtration may be paper, metal, etc., and may be performed multiple times in parallel or in series.

For the filtration, it is preferable to use a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

In this method, agglomerates remaining at the time of particle dispersion and agglomerates generated upon addition of the main dope are only aggregated by using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. Can be removed. In the main dope, the concentration of particles is sufficiently thinner than that of the additive solution, so that the aggregates do not stick together during filtration and the filtration pressure does not increase suddenly.

The acrylic resin (A), cellulose acylate resin (B), and acrylic particles (C) used in the present invention may be dissolved by adding a solvent after adding one or more kinds of powder into a container. The powder may be put in, may be added simultaneously, or may be mixed separately after mixing. Further, it may be added after dissolving only 1 part separately. The order of addition is not particularly limited, and the dissolution temperature and the number of stirring are not particularly limited.

As a method of charging the acrylic resin (A), cellulose acylate resin (B), and acrylic particles (C) used in the present invention into the container, it may be directly input from the upper part of the container. preferable.

FIG. 1 is a diagram schematically showing a dope preparation step, a casting step, and a drying step of a solution casting film forming method preferable for the present invention.

If necessary, large aggregates are removed from the acrylic particle charging vessel 41 with a filter 44 and fed to the stock tank 42. Thereafter, the acrylic particle additive solution is added from the stock tank 42 to the main dope dissolving kettle 1.

Thereafter, the main dope solution is filtered by the main filter 3, and an ultraviolet absorbent additive solution is added in-line from 16 to this.

In many cases, the main dope may contain about 10 to 50% by weight of recycled material. The return material may contain acrylic particles. In that case, it is preferable to control the addition amount of the acrylic particle addition liquid in accordance with the addition amount of the return material.

The additive solution containing acrylic particles preferably contains 0.5 to 10% by mass of acrylic particles, more preferably 1 to 10% by mass, and more preferably 1 to 5% by mass. Most preferably.

The lower the acrylic particle content, the easier it is to handle with a low viscosity, and the higher the acrylic particle content, the smaller the addition amount and the easier the addition to the main dope.

The return material is a product obtained by finely pulverizing the optical film, which is generated when the optical film is formed, and is obtained by cutting off both sides of the film, or by using an optical film original that has been speculated out due to scratches, etc. .

In addition, acrylic resin, cellulose acylate resin, and in some cases, acrylic particles kneaded into pellets can be preferably used.

2) Casting process An endless metal support 31, such as a stainless steel belt or a rotating metal drum, which feeds the dope through a liquid feed pump (for example, a pressurized metering gear pump) to the pressure die 30 and transfers it indefinitely. This is a step of casting a dope from a pressure die slit to a casting position on a metal support.

In the production process of the present invention, plural kinds of dopes may be fed, or a single dope may be fed. When a plurality of dopes are fed, a dope replacement time is provided when switching the dopes. The replacement is performed until the influence of the previous dope is eliminated, but a shorter time is preferable.

The die used in the present invention is preferably a pressure die that can adjust the slit shape of the die base and can easily make the film thickness uniform. The pressure die includes a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

3) Solvent evaporation step In this step, the web (the dope is cast on the casting support and the formed dope film is called a web) is heated on the casting support to evaporate the solvent.

To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. High efficiency and preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or heat by means such as infrared rays.

From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

The temperature at the peeling position on the metal support is preferably 10 to 40 ° C., more preferably 11 to 30 ° C.

The residual solvent amount at the time of peeling of the web on the metal support at the time of peeling is preferably peeled in the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. When peeling off at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be impaired, and slippage and vertical stripes are likely to occur due to peeling tension, so the balance between economic speed and quality The amount of residual solvent is determined.

The amount of residual solvent in the web is defined by the following formula.

Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

The peeling tension at the time of peeling the metal support from the film is usually 196 to 245 N / m. However, if wrinkles easily occur at the time of peeling, it is preferable to peel with a tension of 190 N / m or less. It is preferable to peel at a minimum tension of ˜166.6 N / m, and then peel at a minimum tension of ˜137.2 N / m, and particularly preferable to peel at a minimum tension of ˜100 N / m.

In the present invention, the temperature at the peeling position on the metal support is preferably −50 to 40 ° C., more preferably 10 to 40 ° C., and most preferably 15 to 30 ° C.

5) Drying and stretching step After peeling, a drying device 35 that alternately conveys the web through a plurality of rolls arranged in the drying device and / or a tenter stretching device 34 that clips and conveys both ends of the web with a clip are used. And dry the web.

The drying means is generally to blow hot air on both sides of the web, but there is also a means to heat by applying microwaves instead of wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of residual solvent. Throughout, drying is generally performed at 40-250 ° C. In particular, drying at 40 to 160 ° C. is preferable.

When using a tenter stretching apparatus, it is preferable to use an apparatus capable of independently controlling the film gripping length (distance from the start of gripping to the end of gripping) by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

It is also preferable to provide a neutral zone between different temperature zones so that each zone does not cause interference.

The stretching operation may be performed in multiple stages, and it is also preferable to perform biaxial stretching in the casting direction and the width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise.

In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferred draw ratio for simultaneous biaxial stretching can be in the range of x1.01 to x1.5 in both the width direction and the longitudinal direction.

When the tenter is used, the amount of residual solvent in the web is preferably 20 to 100% by mass at the start of the tenter, and drying is preferably performed while the tenter is applied until the amount of residual solvent in the web is 10% by mass or less. More preferably, it is 5% by mass or less.

When performing the tenter, the drying temperature is preferably 30 to 150 ° C, more preferably 50 to 120 ° C, and most preferably 70 to 100 ° C.

In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C. Is more preferable, and within ± 1 ° C. is most preferable.

6) Winding step This is a step of winding the optical film by the winder 37 after the residual solvent amount in the web is 2% by mass or less, and the dimensional stability is achieved by setting the residual solvent amount to 0.4% by mass or less. A film with good properties can be obtained.

As a winding method, a generally used one may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc., and these may be used properly.

The optical film according to the present invention is preferably a long film. Specifically, the optical film has a thickness of about 100 m to 5000 m, and is usually in the form of a roll. The film width is preferably 1.3 to 4 m, more preferably 1.4 to 2 m.

The film thickness of the optical film according to the present invention is not particularly limited, but when used for a polarizing plate protective film described later, it is preferably 20 to 200 μm, more preferably 25 to 100 μm, and 30 to 80 μm. It is particularly preferred.

<Polarizing plate>
The polarizing plate can be produced by a general method. It is preferable that an adhesive layer is provided on the back side of the optical film according to the present invention, and is bonded to at least one surface of a polarizer produced by immersing and stretching in an iodine solution.

The film may be used on the other surface, or another polarizing plate protective film may be used. For example, commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KV8UY-HA, KV8UX-RHA, KV8UX-RHA Etc.) are preferably used.

A polarizer, which is a main component of a polarizing plate, is an element that transmits only light having a plane of polarization in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

The polarizer is formed by forming a polyvinyl alcohol aqueous solution into a film and dyeing the film by uniaxial stretching or dyeing or uniaxially stretching, and then performing a durability treatment with a boron compound.

As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer, a pressure-sensitive adhesive having a storage elastic modulus at 25 ° C. in the range of 1.0 × 10 ⁴ Pa to 1.0 × 10 ⁹ Pa in at least a part of the pressure-sensitive adhesive layer is used. It is preferable to use a curable pressure-sensitive adhesive that forms a high molecular weight body or a crosslinked structure by various chemical reactions after the pressure-sensitive adhesive is applied and bonded.

Specific examples include, for example, urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, polyether methacrylate types, Examples include anaerobic pressure-sensitive adhesives such as ester-based methacrylate type and oxidized polyether methacrylate, cyanoacrylate-based instantaneous pressure-sensitive adhesives, and acrylate-peroxide-based two-component instantaneous pressure-sensitive adhesives.

The above-mentioned pressure-sensitive adhesive may be a one-component type or a type in which two or more components are mixed before use.

The above-mentioned pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solvent type. The concentration of the pressure-sensitive adhesive liquid may be appropriately determined depending on the film thickness after adhesion, the coating method, the coating conditions, and the like, and is usually 0.1 to 50% by mass.

<Liquid crystal display device>
By incorporating the polarizing plate bonded with the optical film according to the present invention into a liquid crystal panel, various liquid crystal display devices having excellent visibility can be produced. The polarizing plate is bonded to the liquid crystal cell via the adhesive layer or the like.

The polarizing plate according to the present invention is a reflective type, transmissive type, transflective type LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type, etc. Preferably used. In particular, in a large-screen display device having a screen of 30 or more, especially 30 to 54, there is no white spot at the periphery of the screen and the effect is maintained for a long time.

In addition, there was little color unevenness, glare and wavy unevenness, and the eyes were not tired even after long hours of viewing.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example A
<Production of Optical Film Comparative Example 1>
(Dope solution composition)
Acrylic resin Dianar BR85 (Mitsubishi Rayon Co., Ltd.)
70 parts by mass Cellulose acylate resin CAP482-20 (acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 200000 manufactured by Eastman Chemical Co., Ltd.) 30 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The above composition was sufficiently dissolved while heating to prepare a dope solution.

(Film formation of optical film comparative example 1)
The produced dope liquid was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the residual solvent amount reached 100%, and the film was peeled off from the stainless steel band support with a peeling tension of 162 N / m.

The web of the peeled optical film was evaporated at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while stretching 1.1 times in the width direction with a tenter.

After stretching with a tenter and relaxing at 130 ° C for 5 minutes, drying was completed while transporting the drying zone at 120 ° C and 130 ° C with a number of rolls, slitting to a width of 1.5 m, and 10 mm wide at both ends of the film. An optical film comparative example 1 having a thickness of 60 μm and a winding length of 4000 m was obtained by applying a knurling process of 5 μm and winding it around a 6-inch inner diameter core with an initial tension of 220 N / m and a final tension of 110 N / m.

The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.1 times.

<Preparation of Optical Film Comparative Example 2>
Optical film comparative example in the same manner as optical film comparative example 1 except that 0.0008 parts by weight of methyl methacrylate was used as a solvent of the above-mentioned dope solution composition and mixed with methylene chloride and ethanol in the same amounts as in comparative example 1. 2 was produced.

<Preparation of optical film Example 1>
Optical film example as in optical film comparative example 1 except that 0.2000 parts by weight of methyl methacrylate was mixed with methylene chloride and ethanol in the same amounts as in comparative example 1 as the solvent of the above dope composition. 1 was produced.

<Production of Optical Film Comparative Examples 3 to 31>
Production of optical film comparative example 2 except that the mixing ratio of acrylic resin (A) and cellulose acylate resin (B) and the addition amount of methyl methacrylate, methyl acetate, methyl ethyl ketone and hexane as solvents are changed as shown in Table 1. Optical film comparative examples 3 to 31 were produced in the same manner as described above.

<Preparation of Optical Film Examples 2 to 12>
Production of optical film Example 1 except that the mixing ratio of acrylic resin (A) and cellulose acylate resin (B) and the addition amounts of methyl methacrylate, methyl acetate, methyl ethyl ketone, and hexane as solvents were changed as shown in Table 1. In the same manner, optical film examples 2 to 12 were produced.

<Evaluation>
The following evaluation was carried out using the optical film examples 1 to 12 and the comparative examples 1 to 31 produced as described above.

<Quantification of solvent content>
The contents of the ester solvent, the ketone solvent, and the aliphatic solvent according to the present invention in the optical film were quantified by the headspace gas chromatography described above.

<Ductile fracture>
An optical film conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH is cut out at 100 mm (length) × 10 mm (width) under the same conditions, with a radius of curvature of 0 mm and a folding angle of 180 at the center in the vertical direction. The film was folded once in a mountain fold and a valley fold so that the films were exactly overlapped at 0 °, and this evaluation was measured three times and evaluated as follows. In addition, breaking of evaluation here represents having broken into two or more pieces.

○: Cannot be folded 3 times ×: Can be folded at least 1 out of 3 times The samples of Examples 1 to 12 are all evaluated as ○ in the above evaluation, and should be optical films without ductile fracture confirmed. On the other hand, the optical films of Comparative Examples 13 and 14 composed only of acrylic resin were evaluated as x.

<Slipperiness>
Each of the film samples prepared above was conditioned in an air-conditioned room at 23 ° C. and 55% RH for 24 hours, and then one film sample was subjected to the dynamic friction coefficient friction measuring instrument TR type (Toyo) under the same conditions in accordance with JIS K7125-1999. Measured using Seiki).

<Dope state>
Each prepared dope was sampled, allowed to stand at room temperature for 1 day, and observed.

○: No change before standing ×: Precipitation occurred

From Comparative Examples 1 to 4 and Examples 1 and 2, it can be seen that the slipperiness can be improved by containing 0.1% by mass or more of methyl methacrylate in the optical film. Moreover, it turns out that a precipitate generate | occur | produces in dope by containing 1.0 mass% or more.

From the results of Comparative Examples 1 to 16 and Examples 1 to 6, the above effects were obtained when the ratio of cellulose to acrylic was 20/80 to 80/20. However, in the case of an optical film composed only of cellulose or acrylic, methacrylic acid was used. Similar results were not obtained even when methyl acid was added.

Therefore, it was found that the above effect can be obtained only when the ratio of cellulose to acrylic is 20/80 to 80/20.

As can be seen from Comparative Examples 17 to 31 and Examples 7 to 12, similar effects were obtained with methyl acetate, methyl ethyl ketone, and hexane.

Therefore, at least one solvent selected from an ester solvent, a ketone solvent, and an aliphatic solvent in an optical film containing 20 to 80% by mass of a cellulose acylate resin and 20 to 80% by mass of an acrylic resin. It can be seen that the inclusion of 0.1% by mass or more and less than 1.0% by mass improves the slipperiness and makes it possible to produce an optical film with good storage stability of the dope.

Example B
In the same manner as in Examples 7 to 12, the same effect was obtained even when an additive such as ethyl acetate, cyclohexanone, cyclohexane or the like was used instead of methyl acetate, methyl ethyl ketone, or hexane.

Example C
<Preparation of polarizing plate>
A polarizing plate using the optical films of Examples 1 to 12 as a polarizing plate protective film was produced as follows.

A 120 μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched in the transport direction 5 times at 50 ° C. to form a polarizing film.

Next, after applying a corona treatment to the optical film of Example 1 produced in Example A using an acrylic adhesive on one side of the polarizing film, it was bonded.

Further, KC8UCR-5 manufactured by Konica Minolta Opto Co., Ltd., which is an alkali saponified retardation film, was bonded to the other surface of the polarizing film and dried to prepare a polarizing plate P1. Similarly, polarizing plates P2 to P12 were produced using the optical films of Examples 2 to 12.

The polarizing plate using the optical film according to the present invention was excellent in slipperiness and easy to process.

<Production of liquid crystal display device>
Display characteristics of the optical film according to the present invention were evaluated using the prepared polarizing plate.

Remove the pre-bonded polarizing plates on the 32 inch TV 32H2000 manufactured by Toshiba Corporation, and bond the prepared polarizing plates in advance so that KC8UCR-5 is on the glass surface side of the liquid crystal cell. The liquid crystal display devices were each fabricated by bonding so that the absorption axis was in the same direction as the polarizing plate.

The liquid crystal display device produced as described above was found to be a liquid crystal display device with good visibility with reduced color shift and excellent front contrast.

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock tank 5, 14 Liquid feed pump 8, 16 Conduit 10 Ultraviolet absorber charging pot 20 Merge pipe 21 Mixer 30 Die 31 Metal support 32 Web 33 Peeling position 34 Tenter Stretching Device 35 Drying Device 41 Particle Charger 42 Stock Tank 43 Pump 44 Filter

Claims (4)

1. In an optical film containing 20 to 80% by mass of a cellulose acylate resin and 20 to 80% by mass of an acrylic resin,
   An optical film comprising 0.1% by mass or more and less than 1.0% by mass of at least one solvent selected from an ester solvent, a ketone solvent, and an aliphatic solvent.
2. A method for producing the optical film according to claim 1,
   Cellulose acylate resin and acrylic resin, methylene chloride, alcohol,
   A method for producing an optical film, wherein a dope is produced by dissolving in a mixed solvent of at least one solvent selected from methyl methacrylate, an ester solvent, a ketone solvent, and an aliphatic solvent.
3. A liquid crystal panel produced using the optical film according to claim 1.
4. An image display device produced using the liquid crystal panel according to claim 3.

Images